1. Field of the Invention
The present invention relates to a film-forming composition and, more particularly, to a film-forming composition suitable as an interlayer dielectric material in the manufacture of semiconductor devices, exhibiting excellent relative dielectric constant characteristics and moisture-absorption characteristics, capable of forming coatings with a small vacant space size, and exhibiting superior storage stability.
2. Description of the Background Art
Conventionally, silica (SiO2) films formed by a vacuum process such as a CVD process have been extensively used as an interlayer dielectric in the manufacture of semiconductor devices and the like. In recent years, an SOG (spin on glass) film which is a coating-type insulating film made from a composition containing tetraalkoxysilane hydrolyzate as a major component is used with the objective of forming a homogeneous interlayer dielectric. As high integration of semiconductor devices has advanced, an interlayer dielectric with a low relative dielectric constant made from a composition containing polyorganosiloxane as a major component, which is called an organic SOG, has been developed.
However, demand for further integration and layer multiplication of semiconductor devices requires more excellent electric insulation among conductors. Development of a more excellent interlayer dielectric material having a lower relative dielectric constant and exhibiting superior crack resistance is thus strongly desired.
WO 99/03926 discloses a composition for manufacturing an insulating layer for a multi-layer interconnect structure for semiconductor devices with a low relative dielectric constant. This Patent Application discloses a composition comprising a silica component and a thermally decomposable polymer which are dissolved in a specific solvent.
It is, however, difficult for the composition disclosed in WO 99/03926 to maintain adequate mutual affinity among the solvent, thermally decomposable polymer, and silica component, to maintain the micro-layer separation structure after vaporization of the solvent, and to produce a product with homogeneous small vacant spaces after heat treatment. If the mutual affinity between the thermally decomposable polymer and silica component is inadequate, it is difficult to obtain films with a smooth surface by rotation application.
The present invention has been achieved in view of the above situation and has an object of providing a film-forming composition suitable as an interlayer dielectric material in the manufacture of semiconductor devices, which exhibits superior storage stability and can form coatings with an appropriate homogeneous thickness, exhibiting excellent relative dielectric constant characteristics and moisture-absorption characteristics, and having a small vacant space size.
Specifically, the present invention provides a film-forming composition comprising:
(A) at least one silane compound selected from the group consisting of a compound shown by the following formula (1), a compound shown by the following formula (2), and a compound shown by the following formula (3) and a hydrolysis condensate of these compounds:
R2R3Si(OR1)2xe2x80x83xe2x80x83(1)
R2Si(OR1)3xe2x80x83xe2x80x83(2)
Si(OR1)4xe2x80x83xe2x80x83(3)
wherein R1, R2, and R3 individually represent a monovalent organic group,
(B) a polyether shown by the formula (PEO)pxe2x80x94(PPO)qxe2x80x94(PEO)r, wherein PEO represents a polyethylene oxide unit, PPO represents a polypropylene oxide unit, p is a number of 2-200, q is a number of 20-80, and r is a number of 2-200, and
(C) an organic solvent.
The component (A) in the above film-forming composition preferably comprises a hydrolysis condensate of one or more silane compounds selected from the group consisting of a compound of the above formula (1), a compound of the above formula (2), and a compound of the above formula (3).
In the above film-forming composition, the hydrolysis condensate is preferably prepared by a hydrolysis condensation reaction of the above silane compounds in the presence of water and a catalyst.
The above catalyst for the hydrolysis condensation reaction is preferably selected from the group consisting of a metal chelating compound, an organic acid, an inorganic acid, an organic base, and an inorganic base.
The above hydrolysis condensation reaction is preferably carried out further in the presence of an organic solvent (C).
The above hydrolysis condensate is preferably a hydrolysis condensate of silane compounds which comprise a compound of the formula (2).
The above hydrolysis condensate is a hydrolysis condensate of silane compounds which comprise a compound of the formula (2) and a compound of the formula (3).
In the above hydrolysis condensate, the amount of the compound of the formula (3), in terms by weight of complete hydrolysis condensate, is preferably 5 to 40 wt % of the total amount of the compound of the formula (1), the compound of the formula (2), and the compound of the formula (3).
In the above hydrolysis condensate, the amount by weight of the compound of the formula (2) is greater than the amount of the compound of the formula (3).
In the above film-forming composition, the polystyrene-reduced weight average molecular weight of the component (A) is preferably 500-300,000.
In the above film-forming composition, the polystyrene-reduced weight average molecular weight of the component (B) is preferably 1,000-20,000.
The film-forming composition of the present invention preferably comprises 1-80 parts by weight of the component (B) for 100 parts by weight of the component (A) as an complete hydrolysis-condensate.
In the above film-forming composition of the present invention, the solvent (C) is an alcohol solvent or a ketone solvent, or both.
The present invention further provides a method of forming a film comprising applying any film-forming composition described above onto a substrate to produce a coated film and heating the coated film.
The present invention further provides a method of forming a film comprising applying any film-forming composition described above onto a substrate to produce a coated film, heating the coated film at a temperature less than the decomposition temperature of the component (B) to partly cure the component (A), and heating the coated film at a temperature above the decomposition temperature of the component (B).
The present invention further provides a method of forming a film comprising applying any film-forming composition described above onto a substrate to produce a coated film and heating the coated film at a temperature above the decomposition temperature of the component (B).
The present invention still further provides a low-density cured film prepared by any one of the above methods.
Other objects, features and advantages of the invention will hereinafter become more readily apparent from the following description.